A novel co-occluded binary mixture of Helicoverpa armigera single nucleopolyhedrovirus (HearSNPV) genotypes from Spain is a highly effective insecticide

Abstract: The cotton bollworm, Helicoverpa armigera, is a major polyphagous pest. The Helicoverpa armigera single nucleopolyhedrovirus (HearSNPV) can be an effective agent for control of this insect. In the present study, the genotypic diversity present in two Spanish HearSNPV isolates was evaluated with the aim of identifying mixtures of genotypes with improved insecticidal characteristics. Biological characterization of the different genotypes andco-occluded mixtures revealed that a co-occluded mixture of two genotypes in equal proportions named HearSP1B:LB6 showed the highest insecticidal activity, and therefore was selected as the basis for a bioinsecticide. In order to optimize the conditions for scaled virus production, the effects of several factors on the production of HearSP1B:LB6 occlusion bodies (OB) were evaluated. Results indicated that inoculation of newly molted L5 larvae with an LC80 concentration of OBs followed by rearing at 30 °C resulted in the highest production of OBs. Finally, the insecticidal efficacy and persistence of HearSP1B:LB6 OBs in greenhouse and open-field tomato crops in the Iberian Peninsula were compared to those of two commercial biorational insecticides. Application of HearSP1B:LB6 resulted in similar levels of crop protection to those provided by commercial insecticides against H. armigera in both types of crops. OBs showed good persistence in both crop settings, although persistence was markedly longer in greenhouse crops. We conclude that HearLB6:SP1B deserves to be registered as a biological insecticide for control of H. armigera on tomato crops in this region. The unique HearSP1B:LB6 binary genotypic mixture has been the subject of a patent application (P201430956).